The present invention relates to continuous slab casting of metals, and more particularly to a molten metal delivery nozzle for continuous slab casting which reduces turbulence and premature freezing of the molten metal, thereby improving the surface quality of the resultant casting.
Continuous casting techniques have been used to form slabs or strips of various metals such as aluminum, copper, zinc and steel. Several types of continuous casting machines are known. For example, one type of casting machine comprises an opposing pair of moving continuous belts which form a mold into which molten metal is introduced. U.S. Pat. Nos. 4,602,668, 4,785,873 and 4,798,315 disclose such continuous belt casting machines.
Continuous slab casting machines have also incorporated opposing caterpillar-type molds in place of continuous belts, as shown in U.S. Pat. Nos. 3,774,670, 4,290,477, 4,485,835 and 4,619,309.
Prior art slab casting machines have also incorporated a single flat surface onto which the molten metal is cast. U.S. Pat. No. 4,721,152 discloses one such single-belt continuous casting machine.
A major disadvantage of prior art continuous slab or strip casting machines is the production of castings having poor surface quality due to such factors as molten metal turbulence and premature solidification near the nozzle tip. These problems are thought to result from meniscus instability of the molten metal at the nozzle discharge area. Attempts have been made to reduce meniscus instability by methods such as shrouding the molten metal with inert gas as it exits the nozzle. However, the control of meniscus instability by such methods is difficult and has not resulted in a consistent production of castings having optimum surface quality.
The present invention has been developed in view of the foregoing and to overcome other deficiencies of the prior art.